The present invention relates to the coding and editing of audio and video signals and in particular to producing segments of video material that can be joined together on the fly.
Typically when two video clips are played one after the other the decoder is reset to its start state before it decodes the second clip. This leads to the user seeing the last frame of the first clip frozen on the screen while the decoder reinitializes itself and starts decoding the next. Accompanying the reinitialization there is usually a mute in the audio. This type of title behavior is intrusive for the user, lessening their feeling of immersion within the title.
There is, accordingly, a need for seamless joining in which the transition between the end of one clip and the start of the next is not noticeable to the decoder. This implies that from the user's point of view there is no perceptible change in the viewed frame rate and the audio continues uninterrupted. Applications for seamless video are numerous, some examples from a CD-i perspective include video sequence backgrounds for sprites (computer generated images); an example use of this technique would be an animated character running in front of an MPEG coded video sequence. Another is a series of character-user interactions presented as short seamless clips where the outcome of the interaction will determine which clip appears next. A development of this is interactive motion pictures where the user (viewer) can influence the storyline. Branch points along the path a user chooses to take through the interactive movie should appear seamless, otherwise the user will lose the suspension of disbelief normally associated with watching a movie.